#include <stdio.h>
#include <stdlib.h>
#include <math.h>

struct sj
{
    double x1;
    double x2;
    double x3;
    double y1;
    double y2;
    double y3;
}s1;
int main()
{
    scanf("%lf %lf %lf %lf %lf %lf",&s1.x1,&s1.y1,&s1.x2,&s1.y2,&s1.x3,&s1.y3);
    double a,b,c,p;
    a=sqrt((s1.x1-s1.x2)*(s1.x1-s1.x2)+(s1.y1-s1.y2)*(s1.y1-s1.y2));
    b=sqrt((s1.x1-s1.x3)*(s1.x1-s1.x3)+(s1.y1-s1.y3)*(s1.y1-s1.y3));
    c=sqrt((s1.x2-s1.x3)*(s1.x2-s1.x3)+(s1.y2-s1.y3)*(s1.y2-s1.y3));
    p=(a+b+c)/2;
    printf("%.2lf\n",sqrt(p*(p-a)*(p-b)*(p-c)));
    return 0;
}
